The invention relates to a method for the error-monitored transmission of data over parallel interfaces of a multi-step communication system
In multi-step communication systems, referred to also as multi-hop communication systems, data is transmitted from a transmitting station to an ultimately receiving station either directly or over a multiplicity of intermediate stations or relay stations connected therebetween. As well as being transmitted over a single intermediately connected relay station, the data can also be transmitted over a multiplicity of relay stations connected in series one behind the other, which is referred to also as a multi-hop arrangement. Especially, furthermore, in SFN (SFN: Single Frequency Network) communication systems, one and the same signal, and hence one and the same set of data, can be received by a plurality of relay stations simultaneously or, as the case may be, with a slight delay, and transmitted directly to the receiving station or to a further relay station jointly, which is to say simultaneously or correspondingly slightly delayed and using the same frequency. Preemphasis or deemphasis methods can be employed here in the relay stations to increase the efficiency. In order to ensure error-free data transmission, use is made of various error detection and error correction methods, for example an automatic request to repeat the transmission of an original or modified data packet (ARQ: Automatic Repeat Request), which are known per se from communication systems of the type or from other communication systems. The use of what is termed a cyclic redundancy check (CRC) is also known. The methods are applied anew to each individual transmission, which is to say to each transmission from the transmitting station to an adjacent relay station, to each transmission from one relay station to another relay station, and to each transmission from a relay station to the receiving station. Although this approach indeed ensures that the data will reach the receiving station as error-free as possible over a maximum number of paths, the high level of computing power and time expenditure associated therewith is disadvantageous. The approach is furthermore highly energy-intensive since, on the one hand, the unpacking, decoding, and checking of received data in the relay stations and the requesting of a retransmission, or repeated encoding and onward transmission, are processes that consume energy and, on the other hand, the repeated transmission of re-sent data packets finally likewise consumes energy.
WO 01/15374 A1 discloses a method for transmitting an alarm message wherein, if a first transmitter is outside the range of the target receiver, the message is transmitted repeatedly by one or more other transceiver units located within range until the reception of the message by the target receiver is acknowledged by an acknowledgement signal.
U.S. Pat. No. 4,882,765 discloses a method wherein a repeater station automatically retransmits a message to the receiving station on the basis of a preset number of already completed retransmissions by the transmitting station or on the basis of an acknowledgement not received from the receiving station.
Finally, WO 00/74306 A2 discloses a system having a plurality of nodes wherein each node hands off a message received from another node to a subsequent node. In this scheme all the nodes use the same reference frequency.